//-----------------------------------------------------------------------------
// mur_mur_hash2, by Austin Appleby

// Note - This code makes a few assumptions about how your machine behaves -

// 1. We can read a 4-byte value from any address without crashing
// 2. sizeof(int) == 4

// And it has a few limitations -

// 1. It will not work incrementally.
// 2. It will not produce the same results on little-endian and big-endian
//    machines.

#ifndef TAIR_HASH_H
#define TAIR_HASH_H

inline unsigned int mur_mur_hash2 ( const void * key, int len, unsigned int seed )
{
   // 'm' and 'r' are mixing constants generated offline.
   // They're not really 'magic', they just happen to work well.

   const unsigned int m = 0x5bd1e995;
   const int r = 24;

   // Initialize the hash to a 'random' value

   unsigned int h = seed ^ len;

   // Mix 4 bytes at a time into the hash

   const unsigned char * data = (const unsigned char *)key;

   while(len >= 4)
   {
      unsigned int k = *(unsigned int *)data;

      k *= m;
      k ^= k >> r;
      k *= m;

      h *= m;
      h ^= k;

      data += 4;
      len -= 4;
   }

   // Handle the last few bytes of the input array

   const int8_t *idata = (const int8_t *)data;
   switch(len)
   {
      case 3: h ^= idata[2] << 16;
      case 2: h ^= idata[1] << 8;
      case 1: h ^= idata[0];
         h *= m;
   };

   // Do a few final mixes of the hash to ensure the last few
   // bytes are well-incorporated.

   h ^= h >> 13;
   h *= m;
   h ^= h >> 15;

   return h;
}
#endif
